The Spellmaster PBEM. Now in its 2nd edition - SpellMaster II - http://web.lemuria.org/SM2/. Many of the finer parts and settings of Neuromancer have been created out of the knowledge I got from playing this great game. If you look for a fantasy setting instead of a sci-fi one, have a look at the site. Very recommended.
I also want to explicitly thank Tom Vogt, the creator of Spellmaster. Some smaller parts of the Neuromancer parser are based on his work.